1. Field of the Invention
This invention relates generally to fuel delivery systems for vehicles, and more particularly to fuel delivery modules housed within a vehicle's fuel tank.
2. Description of the Related Art
Over the past several years, fuel pumps for passenger automobiles and light trucks have changed from a mechanical engine-mounted device to an electrically-operated gear pump or turbine pump mounted in the fuel tank of the vehicle. Conventional gear or turbine fuel pumps are typically located at the bottom center of the tank, as opposed to off to one side of the tank. This bottom center location ensures that the maximum amount of fuel is available to the pump even when the fuel level is low and minimizes fuel starvation of the fuel pump as the fuel sloshes from one side of the tank to the other during vehicle cornering, braking, or accelerating, or when driving or parking on a slope.
Fuel starvation occurs when the inlet of the fuel pump is not immersed in fuel, and the fuel pump sucks air or vapor rather than fuel. Fuel pump starvation results in engine stammer or stalling or engine start-up difficulty and is of particular concern in later model vehicles having fuel injected engines, due to the precise metering and timing requirements of injecting fuel into the fuel/air intake ports of the engine cylinders.
In an attempt to overcome the problem of fuel pump starvation during vehicle operation, baffles were often welded or formed into the fuel tanks to restrain a portion of the fuel from "sloshing" away from the fuel pump during vehicle maneuvering, thus keeping the fuel pump inlet immersed in fuel at all times. Such attempts met with limited success. Today, most fuel tanks are manufactured from puncture-resistant, rubberized plastic and no longer utilize baffles due to the limited success of their intended purpose, the difficulty in manufacturing, and added cost. Instead, most conventional vehicles now utilize electrically operated passive fuel delivery modules that have a fuel reservoir from which fuel can be drawn from during times when vehicle maneuvering forces the tank fuel away from the fuel pump inlet.
Passive fuel delivery modules are comprised of a gear or turbine fuel pump, a housing which surrounds the fuel pump and acts as a fuel reservoir from which the pump can draw during times when the fuel is forced away from the fuel pump during vehicle operation, and a pressure regulator and valve assembly which is in fluid communication with the fuel injectors. Conventional passive fuel delivery modules require a check valve or float valve to prevent the reservoir fuel from escaping the reservoir. These check valves or float valves not only add to the cost of the fuel delivery module, but the valves can fail, resulting in additional maintenance or replacement expense. Further, current fuel delivery modules only filter the fuel coming from the main fuel tank, not the reservoir fuel. By only filtering one stage of the fuel delivery module, the pump may be exposed to debris or contaminants in the reservoir fuel which could damage the pump. Therefore, it should be appreciated that an improved passive fuel delivery module is required in the industry that eliminates the need for check valves or float valves to maintain fuel in the reservoir, and an improved passive fuel delivery module that filters both the reservoir fuel and the tank fuel before the fuel enters the fuel pump.
In addition to the above mentioned drawbacks of conventional passive fuel delivery modules, another problem deals with their suspension within the fuel tank. As discussed above, most fuel pumps and/or the later devised passive fuel delivery modules are located at the bottom center of the fuel tank. With steel fuel tanks, the mounting or suspension of the pumps and/or fuel delivery modules was not of particular concern. However, as mentioned above, most fuel tanks are now manufactured from puncture-resistant rubberized plastic. These plastic fuel tanks are less rigid than the previous steel tanks and therefore tend to deflect more when loaded with fuel. As such, the fuel pumps and/or fuel delivery modules must be mounted or suspended in such a way as to allow them to vertically displace with the bottom of the fuel tank. One type of such a suspension system utilizes vertically disposed slide rails suspended from the top of the fuel tank. The fuel pump and/or fuel delivery module slides up and down on these rails as the bottom of the tank vertically deflects. A passive fuel delivery module mounted in such a way is difficult and time consuming to service. Therefore, an improved suspension system is needed in the industry that enables the passive fuel delivery module to be easily removed and installed for routine maintenance and servicing.
Additionally, current designs of the passive fuel modules and the pressure regulator assemblies attached thereto are difficult to access for repair and maintenance. Therefore, it is desirable to have a passive fuel module and fuel pressure regulator combined in a single unit which is can be easily removed and installed in the fuel tank for routine maintenance and servicing.
Therefore, those familiar with fuel delivery modules recognize the need for an improved passive fuel delivery module which eliminates the need for check valves or float valves, which has an improved suspension mechanism, and which can be easily removed from the tank for repair and maintenance.